Rubber cement for flocked fabrics



Patented Dec. 12, 1944 RUBBER CEMENT roa FLOCKED FABRICS Glen Sei'tonHiers, Bala-Cynwyd, Pa... assignor to Collins & Aikman Corporation,Philadelphia, I Pa., a corporation of Delaware No Drawing. ApplicationMarch 29, 1941, Serial No. 385,859

4 Claims. (01. 260-165) g This invention relates to adhesives which arecharacterized by high resistance to tear and/or to abrasion and yet aresuflicientlyflexible for use on flocked pile fabrics.

According to my improvements I obtain superior results when as isusualcotton or viscose fibers are used as the pile fiock, but theseimprovements are particularly important in connection with securing pileforming wool flock to a base fabric on which my adhesive has beenapplied.

Solvent rubber cements, ordinarily used for bonding ground or cutfibrous materials to a fabric base in the preparation of suede or pileflock fabrics, contain various types of inorganicv fillers such asclays, whiting, barytes, zinc oxide and occasionally the organicmaterial carbon black. These are added for the purpose of cheapening thecompound by increasing its volume, thus permitting a given amount ofrubber to cover a greater area when spread as a thin cement. Thisextension of its coverage has given rise to the use of the term"extenders" for materials of this class. Many times these "extenders areadded to a cement; for the purpose of imparting special properties. Theaddition of whiting, for example, produces soft flexible films, and forthis reason is much used by converters who wish to produce coatedfabrics which are not too stiff. Some of the clays also impart this 0closed, the effects are cumulative.

property of good flexibility. Zinc oxide, barytes and carbon black aresometimes used to produce smooth spreading cement. These last namedfillers produce good tensile strength and fair resistance to abrasion.For resistance to abrasion and tear, carbon black has been consideredthe best of prior fillers but has the disadvantage of restricting thecolor range.

Cotton and viscose are the fibers which are usually used for makingflocked fabrics. Many rubber cements of fair spreading qualities can beused for bonding these fibers because they are readily anchored. Theyare essentially straight fibers and so can be tightly packed into agiven area, especially if some means is used to insure an erectposition. These fibers packed closely together tend to reenforce oneanother against displacement.

Flock from wool and most other fibers of animal origin are usually notstraight but are curved. Examination under a microscope proves wool tobe crescent shaped. Because of this configuration it is diilicult topack wool fibers close together when they areconverted into flockedfabrics and unless some special means, as in my .or crescent shaped, anda subsequent overflocking with shorter wool fibers, with straight fibersor with ground flock, each of which types of flock will sift through theinitially applied wool even when the wool has been applied to themaximum degree to which application of wool flock is possible. Thesubsequently applied flock obviously gives visual efiects dependent ontheir type and color, and in addition to this, increases resistance ofthe adhesive to tear or peeling.

When used with the specific adhesives herein dis- As stated in the priorapplication, a particularly desirable fabric has a pile portion of woolflock cut to substantially 1 lengths and a shorter flock of casein woolfiber cut to substantially M lengths. The wool flock is applied tosubstantially the maximum amount which can be applied by the fiockingoperation used, and the synthetic shorter and straighter fibers areapplied uniformly in the same manner but over and through the initiallyapplied flock, whereby, because of its flocking characteristics, it willpenetrate the longer flock and be secured to the base by the sameanchoring adhesive.

In addition to improving the coverage of the backing fabric the short.fibers improve the bond of the longer fibers, greatly reduce thetendency of the adhesive to peel or tear, and increase the wearabilityas measured by standard rub testing machines by several hundred percent.

, The cements which have heretofore been used to anchor viscose andcotton flock are not satisfactory for anchoring wool flock to a basematerial such as cotton. This is due in part to the curved shape of thewool flock, which prevents the packing of great numbers of fibers into agiven area on the base fabric, and in part to the' common characteristicof these fillers, aside from their very fine state of division, is thatthey are hard particles which may be classed as abrasives.

These microscopic particles, which may vary from one micron down toone-twentieth of a micron or even less particle size, ofier a remarkableresistance to the sliding of wool fibers through and out of the cementwhen the ends of the fibers are in contact with the cement, as inflocked pile fabrics.

The films may be made still more resistant to abrasion by theincorporation of small amounts of certain hydrocarbon resins which arecharacterized by their toughness but which are compatible with rubber,

It appears that the surface serrations of the wool formed by theoverlapping of the epithelial scales become enmeshed in the mass offinely divided particles, and as a result the wool is held in theadhesive very much more firmly than the wool which is bonded by rubbercements containing ordinary fillers. The cements may, of course, containsuitable accelerators, antioxidants and solvents.

The fillers which I have found to impart to rubber cements these unusualproperties, all have s in common a low specific gravity and are veryfinely divided. Examples are specially prepared calcium carbonate, knownas Kalvan, specially prepared calcium carbonate known as Calcene,specially prepared calcium silicate known as Silene, and speciallyprepared hydrated aluminum oxide known as aluminum hydrate. Thesematerials may be blended with rubber and in-' timately mixed therewithon a rubber mill, after which the rubber and filler is dispersed in anaqueous or other liquid medium to form rubber cements. The dry rubberused may be natural, such as pale crepe and smoked sheet, or syntheticrubber such as Neoprene. Both natural and synthetic rubber will bereferred to in the claims as rubber.

An object of my invention is to provide an improved natural or syntheticrubber cement which is resistant to tear and abrasion.

Another obiect is to provide a rubber cement in which hard finelydivided abrasive materials are incorporated in the rubber before therubber is dispersed in a liquid medium.

Another object is to provide a rubber cement having hard very finelydivided abrasive material and a tough hydrocarbon resin compatible withrubber intimately mixed with the rubber.

Another object is to provide a flocked pile fabric having a wool fiockface which is secured to a backing by my improved adhesive.

Another object is to provide a rubber adhesive which is resistant totear and abrasion and which may be dyed any desired color.

Another object is to incorporate finely divided abrasive material havingparticle size of one micron or less in rubber on a rubber mill andthereafter dispersing the mass in a liquid medium.

Another object is to provide a rubber cement in which hard very finelydivided abrasive materials having a low specific gravity and bulkingvalues ranging from 15 to 21 pounds per cubic foot are intimately mixedwith the rubber and dispersed therewith.

These and other objects will be manifest from a consideration of thefollowing description and claims.

According to my improvements, I incorporate finely divided abrasivefillers, which are considered inferior to carbon black as a tearresistant producer for molded rubber articles, and provide a rubbercement for bonding wool flock which is superior to rubber cementsdepending on carbon black to provide resistance to abrasion and tear.Small proportions of carbon black may, of course, be used for its colorproducing properties if desired. If no coloring matter is added thecement will be translucent or it can be colored as desired.

I prepare my cement by taking the various compounding ingredients andmilling them together to an intimate mixture in a standard rubber millor mixer by established mixing procedures. If it is desired to convertthese compounds into cements of the solvent rubber type, the milledcomposition is brought into contact with a suitable solvent mixture in amixer oi. the churn or dough mixer type and milled to a smoothhomogeneous mass of suitable consistency. If, on the other hand, it isdesired to convert' the composition to an artificial aqueous dispersion,this may be accomplished by any one of a number of standard techniques.Sometimes such aqueous dispersions are to be desired, especially inthose procedures for making flocked fabric which use high potentialelectrostatic fields for the deposition or the straightening of the.

flock. In these cases the fire hazard due to the presence of inflammablesolvents is considerable and hence the use of aqueous dispersions ishighly desirable. It is to be understood that these artificialdispersions of milled or synthetic rubber produce a result which cannotbe duplicated or approached by compounding naturally occurring latex. Inthe latter case the addition of reenforcing fillers and aqueousdispersions of tough hydrocarbon resins does not increase the tear orabrasion resistance of the latex film for the reason that thereenforcing particles do not become an integral part of the rubber film.In other words, as viewed through a, microscope, it would be evidentthat particles of rubber were contiguous with particles of filler 0rresin, but the particles would be discrete and separate and so thefiller or resin would merely serve to separate the rubber particles andso to dilute the rubber film by moving the rubber particles furtherapart. The effect would be one of weakening rather than strengthening.

According to my invention, however, films of artificially dispersed millcompositions of the nature of those described above show that themineral filler alone or with the resin is intimately associated with therubber so that each particle contains within it a homogeneous mixture ofrubber, filler and/or resin.

The films of my improved cements when spread on cloth are quite flexiblebut are very resistant to abrasion and to tearing. This may beillustrated by attempting to scratch the surface of a film with a thumbnail. It will be found that the films are very tough and not readilybroken by repeated attempts using all the force of which the thumb iscapable. The same cement formulations containing the usual fillers areeasily abraded and torn open by such treatment.

As stated, it has been further found that these films may be made stillmore resistant to such abrasion by the ii morporation of small amountsof certain resins'which are characterized by their toughness but whichare compatible with rubber. The most remarkable of these resins is oneknown as Marbon B. As little as 5% of this resin on the basis oftherubber imparts considerable increased toughness and resistance totearing.

There is also an increased improvement in the quality or the bondbetween the cement and the wool flock. Another such resin known asIsolac, although somewhat less effective than Marbon B. very definitelyimproves the bonding action of the cement for the fiock and for the samereason. Marbon B and Isolac are tough, thermoplastic, resin-likederivatives of rubber. More specifically "Marbon B is commonly called acyclo or cyclized rubber, which is the result of the treatment of rubberto cause a rearrangement oi. the rubber molecule so as to convert it toa different physical state. The production of this material is disclosedin United States Patent No. 2,230,359. "Isolac" is a chemical derivativeof rubber made by reacting crude rubber with phenol in accordance withthe procedure outlined in United States Patents Nos. 2,158,530 and2,203,597. Both Marbon B" and "Isolac" are the reaction products ofcrude rubber and a phenol in the presence of an acid catalyst.Polystyrene may also be used.

Examples of satisfactory compounds before dispersion for bonding pileforming wool flocks are as follows. All figures refer to parts byweight.

' The compounds of the examples may be combined with suitablehydrocarbon solvents such as solvent naphtha, solvesso or Skelly-solvetypes, aromatics, chlorinated hydrocarbons r alcohols, esters orketones, or they may be prepared as aqueous dispersions by the use ofdispersing agents in a known manner.

Example 1 I Parts Smoked sheet (rubber) 100 Specially prepared calciumcarbonate having a particle size of one micron or less, such as Kalvan125 Sulphur 2 Zinc oxide 3 Accelerators, such as captax and zimate--1.75 Age rite white 1 Telloy 1 Stearic acid l Reogen 1 Example 2 PartsSmoked sheet (rubber) 100 Specially prepared calcium carbonate having aparticle size smaller than one micron, such as Kalvan 100 Marbon B 5Sulphur 0.75 Zinc oxide 5 Butyl 8 3 Age rite white 1 Stearic acid 1Reogen 1 Carbon black 1 Example 3 Parts Smoked sheet (rubber) 100Specially prepared calcium silicate, particle size smaller than onemicron, such Specially prepared hydrated aluminum oxide, particle sizesmaller than one micron, such as aluminum hydrate C-741" Marbon B 10Vulcanizing, accelerating and anti-ageing oxidants in the approximateproportions of the previous example.

Example 6 Parts Smoked sheet. (rubber) 100 Aluminum hydrate 0-741Sulphur 1 Zinc oxide 5 Butyl 8 4 Altax 1 Age rite whit 1 Telloy 1Stearic acid 2 Reogen 1 Carbon black 2 The above examples are allspecific to the use of natural rubber, although satisfactory adhesivesmay be made from synthetic compounds such as Neoprene (type GN) Example7 Parts Neoprene (type GN) 100 Kalvan 100 Zinc oxide 5 Calcined magnesia4 Accelerators a 2 Age rite white- 1 Stearic acid 1 Reogen 1 Carbonblack 1 Example 8 Parts Neoprene (type GN) 100 Kalvan 75 Marbon B 5 andthe other compounding ingredients recited in Example 7 in the samenumber of parts.

As hereinbeiore stated, my finely divided fillers are characterized by alow specific gravity. The specially prepared calcium carbonate (Kalvan)has a specific gravity of 2.65 and a particle size varying from .05 to.2 microns. The bulking value in pounds per cubic foot is 21. Silene hasa specific gravity of 2.25, particle size of from .1 to .4 microns and abulking value 01' from-'15 to 16 pounds per cubic foot. The hydratedaluminum oxides C-740 and 0-741 have a specific gravity of 2.35.particle size of from .1 to .6 microns and a bulking value orapproximately 15 pounds per cubic toot. These materials when compoundedas above described produce superior resistance to tear and abrasion andincrease the adhesion of the rubber cement to the fabric and as hashereinbeiore been stated, provide an excellent bond for pile formingwool flock. In all the examples the flexibility oi the fabric issatisfactory and the cement is translucent, unless pigments are added. I

In general, the natural or synthetic rubber constituent of my cementbeing 100 parts by weight, the Kalvan. Silene or aluminum hydrate C-740and C-741 may be used to the extent 65 to 150 parts. Other recommendedamounts in parts by weight of the compounded ingredi- I parts by weightof a hard abrasive mineral filler as by milling, the particle slzei orsaid hard abrasive mineral tiller being less than one micron and thefiller being any one o! the group consisting of calcium carbonate,calcium silicate and hy-i drated aluminum oxide and aboutLiO parts byweight of a tough thermoplastlc.'resin-like derivative of rubbercomprising the reaction product of crude rubber and a phenol in thepresence 0! an acid catalyst.

2. A flocked pile fabric having a base material,

wool pile flockand a binding material, said binding material being arubber cement which is intlmately mixed with a hard abrasive mineralfiller of the group consisting of calcium carbonate, calcium silicateand hydrated aluminum oxide, the particle size of said hard abrasivemineral filler being less than one micron.

3. In the article of claim 2, said mineral filler being present in thecement to the extent of from to parts based on the dry weight of rubber.

4. In the article of claim 2, said rubber cement containing about 10parts by weight of a tough thermoplastic resin-like derivative of rubbercomprising the reaction product of crude rubber and a phenol in thepresence of an acid catalyst.

GLEN SEFION HIERS.

